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i am new with f# , will be great if some 1 can help , nearly half a day gone solving this problem Thank you
module Certificate =
type T = {
Id: int
IsECert: bool
IsPrintCert: bool
CertifiedBy: string
Categories: Category.T list
}
let createPending now toZonedDateTime toBeCertifiedByName (job: Models.Job.T) (certificateType: Models.CertificateType.T) (pendingCertificate: Models.PendingCertificate.T) visualization (categories: Category.T list) =
let forCompletion = Models.PendingCertificate.getCertificateForCompletion pendingCertificate
{
Id = forCompletion.Id |> CertificateId.toInt
IsECert = Models.PendingCertificate.isECertificate pendingCertificate
IsPrintCert = Models.PendingCertificate.isPrintCertificate pendingCertificate
CertifiedBy = toBeCertifiedByName
Categories = categories}
i am getting an error in "Incomplete structured construct at or before this point"
Your formatting is all off. I will assume here that this is just a result of posting to StackOverflow, and your actual code is well indented.
The error comes from the definition of createPending: this function does not have a result. All its body consists of defining a forCompletion value, but there is nothing after it. Here's a simpler example that has the same problem:
let f x =
let y = 5
This function will produce the same error, because it also doesn't have a result. In F#, every function has to return something. The body cannot contain only definitions of helper functions or values. For example, I could fix my broken function above like this:
let f x =
let y = 5
x + y
This function first defines a helper value y, then adds it to its argument x, and returns the result.
> f 2
> 7
>
> f 0
> 5
How exactly you need to fix your function depends on what exactly you want it to mean. I can't help you here, because you haven't provided that information.
I implemented a <textarea> in Elm such that tabs indent and unindent instead of change focus to another HTML element. Works great except that unindenting sometimes causes the selection to disappear! If I'm selecting the 5th character to the 12th character, I press shift-tab, then it removes 2 tab characters, but it also makes the selection change to a cursor at position 10. The selection range should remain the same..
I have an SSCCE at Ellie: https://ellie-app.com/3x2qQdLqpHga1/2
Here are some screenshots to illustrate the problem. Pressing Setup shows this:
Then pressing Unindent should show the following (with the selection of "def\ng" still intact):
Unfortunately, pressing Unindent actually shows the following. The text is unindented fine, but the selection range goes away and there's just a cursor between the g and the h:
Interesting issue and excellent problem illustration!
The problem is that for some reason re-rendering doesn't occur when one of the selectionStart/selectionEnd properties remains the same. Try changing 5 to 6 on line #42.
It works when you introduce a forced reflow in the element structure. See here: https://ellie-app.com/6Q7h7Lm9XRya1 (I updated it to 0.19 to see if that would solve the problem, but it didn't).
Note that this probably re-renders the whole textarea anew so it might cause problems if the textarea is a huge piece of code. You could solve that by alternating between two identical textareas where you toggle their visibility every render.
module Main exposing (Model, Msg(..), main, update, view)
-- Note: this is Elm 0.19
import Browser
import Browser.Dom exposing (focus)
import Html exposing (Html, button, div, text, textarea)
import Html.Attributes exposing (attribute, class, cols, id, property, rows, style, value)
import Html.Events exposing (onClick)
import Html.Lazy exposing (lazy2)
import Json.Encode as Encode
import Task exposing (attempt)
type alias Model =
{ content : String
, selectionStart : Int
, selectionEnd : Int
-- keep counter of renderings for purposes of randomness in rendering loop
, renderCounter : Int
}
main =
Browser.element
{ init = initModel
, view = view
, update = update
, subscriptions = \s -> Sub.none
}
initModel : () -> ( Model, Cmd Msg )
initModel flags =
( Model "" 0 0 0, Cmd.batch [] )
type Msg
= Setup
| Unindent
| NoOp (Result Browser.Dom.Error ())
update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
let
newRenderCounter =
model.renderCounter + 1
in
case msg of
Setup ->
( { model
| content = "\tabc\n\tdef\n\tghi"
, selectionStart = 5
, selectionEnd = 12
, renderCounter = newRenderCounter
}
, attempt NoOp <| focus "ta"
)
Unindent ->
( { model
| content = "\tabc\ndef\nghi"
, selectionStart = 5
, selectionEnd = 10
, renderCounter = newRenderCounter
}
, attempt NoOp <| focus "ta"
)
NoOp _ ->
( model, Cmd.batch [] )
view : Model -> Html Msg
view model =
div []
(viewTextarea model model.renderCounter
++ [ button [ onClick Setup ] [ text "Setup" ]
, button [ onClick Unindent ] [ text "Unindent" ]
]
)
viewTextarea : Model -> Int -> List (Html msg)
viewTextarea model counter =
let
rerenderForcer =
div [attribute "style" "display: none;"] []
ta =
textarea
[ id "ta"
, cols 40
, rows 20
, value model.content
, property "selectionStart" <| Encode.int model.selectionStart
, property "selectionEnd" <| Encode.int model.selectionEnd
]
[]
in
-- this is the clue. by alternating this every render, it seems to force Elm to render the textarea anew, fixing the issue. Probably not very performant though. For a performant version, use an identical textarea instead of the div and make sure the two selectionStart/end properties both differ from the previous iteration. Then alternate visibility between the two every iteration.
if isEven counter then
[ ta, rerenderForcer ]
else
[ rerenderForcer, ta ]
isEven : Int -> Bool
isEven i =
modBy 2 i == 0
I am playing with records and list. Please, I want to know how to use one variable twice. When I assign any values into variable _list and after that I try rewrite this variable then raising error:
** exception error: no match of right hand side value
-module(hello).
-author("anx00040").
-record(car, {evc, type, color}).
-record(person, {name, phone, addresa, rc}).
-record(driver, {rc, evc}).
-record(list, {cars = [], persons = [], drivers = []} ).
%% API
-export([helloIF/1, helloCase/1, helloResult/1, helloList/0, map/2, filter/2, helloListCaA/0, createCar/3, createPerson/4, createDriver/2, helloRecords/0, empty_list/0, any_data/0, del_Person/1, get_persons/1, do_it_hard/0, add_person/2]).
createCar(P_evc, P_type, P_color) -> _car = #car{evc = P_evc, type = P_type, color = P_color}, _car
.
createPerson(P_name, P_phone, P_addres, P_rc) -> _person= #person{name = P_name, phone = P_phone, addresa = P_addres, rc = P_rc}, _person
.
createDriver(P_evc, P_rc) -> _driver = #driver{rc = P_rc, evc = P_evc}, _driver
.
empty_list() ->
#list{}.
any_data() ->
_car1 = hello:createCar("BL 4", "Skoda octavia", "White"),
_person1 = hello:createPerson("Eduard B.","+421 917 111 711","Kr, 81107 Bratislava1", "8811235"),
_driver1 = hello:createDriver(_car1#car.evc, _person1#person.rc),
_car2 = hello:createCar("BL 111 HK", "BMW M1", "Red"),
_person2 = hello:createPerson("Lenka M","+421 917 111 111","Krizn0, 81107 Bratislava1", "8811167695"),
_driver2 = hello:createDriver(_car2#car.evc, _person2#person.rc),
_car3 = hello:createCar("BL 123 AB", "Audi A1 S", "Black"),
_person3 = hello:createPerson("Stela Ba.","+421 918 111 711","Azna 20, 81107 Bratislava1", "8811167695"),
_driver3 = hello:createDriver(_car3#car.evc, _person3#person.rc),
_list = #list{
cars = [_car1,_car2,_car3],
persons = [_person1, _person2, _person3],
drivers = [_driver1, _driver2, _driver3]},
_list.
add_person(List, Person) ->
List#list{persons = lists:append([Person], List#list.persons) }.
get_persons(#list{persons = P}) -> P.
do_it_hard()->
empty_list(),
_list = add_person(any_data(), #person{name = "Test",phone = "+421Test", addresa = "Testova 20 81101 Testovo", rc =88113545}),
io:fwrite("\n"),
get_persons(add_person(_list, #person{name = "Test2",phone = "+421Test2", addresa = "Testova 20 81101 Testovo2", rc =991135455}))
.
But it raising error when i use variable _list twice:
do_it_hard()->
empty_list(),
_list = add_person(any_data(), #person{name = "Test",phone = "+421Test", addresa = "Testova 20 81101 Testovo", rc =88113545}),
_list =add_person(_list, #person{name = "Test2",phone = "+421Test2", addresa = "Testova 20 81101 Testovo2", rc =991135455}),
get_persons(_list)
.
In the REPL, it can be convenient to experiment with things while re-using variable names. There, you can do f(A). to have Erlang "forget" the current assignment of A.
1> Result = connect("goooogle.com").
{error, "server not found"}
2> % oops! I misspelled the server name
2> f(Result).
ok
3> Result = connect("google.com").
{ok, <<"contents of the page">>}
Note that this is only a REPL convenience feature. You can't do this in actual code.
In actual code, variables can only be assigned once. In a procedural language (C, Java, Python, etc), the typical use-case for reassignment is loops:
for (int i = 0; i < max; i++) {
conn = connect(servers[i]);
reply = send_data(conn);
print(reply);
}
In the above, the variables i, conn, and reply are reassigned in each iteration of the loop.
Functional languages use recursion to perform their loops:
send_all(Max, Servers) ->
send_loop(1, Max, Servers).
send_loop(Current, Max, _Servers) when Current =:= Max->
ok;
send_loop(Current, Max, Servers) ->
Conn = connect(lists:nth(Current, Servers)),
Reply = send_data(Conn),
print(Reply).
This isn't very idiomatic Erlang; I'm trying to make it mirror the procedural code above.
As you can see, I'm getting the same effect, but my assignments within a function are fixed.
As a side note, you are using a lot of variable names beginning with underscore. In Erlang this is a way of hinting that you will not be using the value of these variables. (Like in the above example, when I've reached the end of my list, I don't care about the list of servers.) Using a leading underscore as in your code turns off some useful compiler warnings and will confuse any other developers who look at your code.
In some situations it is convenient to use use SeqBind:
SeqBind is a parse transformation that auto-numbers all occurrences of these bindings following the suffix # (creating L#0, L#1, Req#0, Req#1) and so on.
Simple example:
...
-compile({parse_transform,seqbind}).
...
List# = lists:seq(0, 100),
List# = lists:filter(fun (X) -> X rem 2 == 0 end, List#)
...
I used google...
Erlang is a single-assignment language. That is, once a variable has been given a value, it cannot be given a different value. In this sense it is like algebra rather than like most conventional programming languages.
http://www.cis.upenn.edu/~matuszek/General/ConciseGuides/concise-erlang.html
I have a big list of some forms with data that needs to be concated with other data from others forms with the same name.
The list format is quite complex and looks like this:
[[{EVAL_SEQ_1, {FORMNAME, ListDataToConcat1}}], [{EVAL_SEQ_2, {FORMNAME, ListDataToConcat2}}], ...]
This is the output that I want:
[[{EVAL_SEQ_1, {FORMNAME, ListDataToConcat1 + ListDataToConcat2}}]}}] ...]
Where:
EVAL_SEQ_1 = Form Sequence Number,
FORMNAME = Form Name
ListDataToConcat = List that Needs to concat
eg.Here is my sample data:
[[{"eval_data_12",
{<<"prvl_mobable_asset_0000_h200401">>,
[{'F_01_0100',[1]},
{'F_01_0090',["3"]},
{'F_01_0080',[]},
{'F_01_0070',[9999]},
{'F_01_0060',[{era,0},{year,[]},{month,[]}]},
{'F_01_0050',[]},
{'F_01_0040',[]},
{'F_01_0030',[]},
{'F_01_0020',<<>>},
{'F_01_0010',<<"4 - 8">>}]}}],
[{"eval_data_11",
{<<"prvl_mobable_asset_0000_h200401">>,
[{'F_01_0100',[]},
{'F_01_0090',["2"]},
{'F_01_0080',[]},
{'F_01_0070',[22222]},
{'F_01_0060',[{era,0},{year,[]},{month,[]}]},
{'F_01_0050',[]},
{'F_01_0040',[]},
{'F_01_0030',[]},
{'F_01_0020',<<>>},
{'F_01_0010',<<"4 - 1">>}]}}], ...]
I want the resultant output like this:
[{"eval_data_11",
{<<"prvl_mobable_asset_0000_h200401">>,
[{'F_01_0100',[[], [1]]},
{'F_01_0090',[["2"], ["3"]]},
{'F_01_0080',[[], []]},
{'F_01_0070',[[22222], [9999]]},
{'F_01_0060',[[{era,0},{year,[]},{month,[]}], [{era,0},{year,[]},{month,[]}]]},
{'F_01_0050',[[], []]},
{'F_01_0040',[[], []]},
{'F_01_0030',[[], []]},
{'F_01_0020',[[<<>>], [<<>>]]},
{'F_01_0010',[[<<"4 - 1">>], [<<"4 - 8">>]}]}}]
I propose you this solution:
[edit]
I modified the code to answer your last comment, there are still fuzzy things:
if Assets are different, creates different record list?
if not what should be done with Asset name? I have chosen to keep the "smallest one"
is the order of records important - I decided no
One remark, I am missing some context, but If I add to collect such informations, I would store it in an ets table. It is faster to update, easy to traverse, and easy to transform into list if needed.
-module (t).
-compile([export_all]).
% rec = {atom,term}
% reclist = [rec,...]
% asset = {bin,reclist}
% eval_data = [{list,asset}]
% eval_set = [eval_data,...]
% recs = {atom,[term]}
% recslist = [recs,...]
addrec({Key,Val},Recslist) ->
Val_list = proplists:get_value(Key, Recslist, []),
[{Key,[Val|Val_list]}|proplists:delete(Key,Recslist)].
merge_rec(Reclist,Recslist) -> lists:foldl(fun(Rec,Acc) -> addrec(Rec,Acc) end,Recslist,Reclist).
merge_eval([{Eval,{Asset,Reclist}}],[]) ->
[{Eval,{Asset,[{Key,[Val]} || {Key,Val} <- Reclist]}}];
merge_eval([{Eval,{Asset,Reclist}}],[{Eval_low,{Asset_low,Recslist}}]) ->
[{min(Eval,Eval_low),{min(Asset,Asset_low),merge_rec(Reclist,Recslist)}}].
merge_set(Eval_set) -> lists:foldl(fun(Eval_data,Acc) -> merge_eval(Eval_data,Acc) end,[],Eval_set).
test() ->
Eval_set = [[{"eval_data_10",
{<<"prvl_mobable_asset_0000_h200401">>,
[{'F_01_0100',[1]},
{'F_01_0090',["3"]},
{'F_01_0080',[]},
{'F_01_0070',[9999]},
{'F_01_0060',[{era,0},{year,[]},{month,[]}]},
{'F_01_0050',[]},
{'F_01_0040',[]},
{'F_01_0030',[]},
{'F_01_0020',<<>>},
{'F_01_0010',<<"4 - 8">>}]}}],
[{"eval_data_11",
{<<"prvl_mobable_asset_0000_h200401">>,
[{'F_01_0100',[]},
{'F_01_0090',["2"]},
{'F_01_0080',[]},
{'F_01_0070',[22222]},
{'F_01_0060',[{era,0},{year,[]},{month,[]}]},
{'F_01_0050',[]},
{'F_01_0040',[]},
{'F_01_0030',[]},
{'F_01_0020',<<>>},
{'F_01_0010',<<"4 - 1">>}]}}]],
merge_set(Eval_set).
#trex:
FormList = [[{EVAL_SEQ_1, {FORMNAME, ListDataToConcat1}}], [{EVAL_SEQ_2, {FORMNAME, ListDataToConcat2}}], ....]
You will need to get a separate the list which has common form names as <<"prvl_mobable_asset_0000_h200401">>
{MobableList, EvalDataList} = lists:partition(fun([{EVAL_SEQ, {FORMNAME, ListData}}]) ->
FORMNAME == <<"prvl_mobable_asset_0000_h200401">>
end, FormList),
Then, Get a separate Tuple of Form sequences and Lists. To separate them
{EvalSeq, MergingList} = lists:foldl(fun(X, {EvalNames, OutList}) ->
[{EVAL_SEQ, {FORMNAME, ListData}}] = X,
{[EVAL_SEQ|EvalNames], [ListData|OutList]}
end, {[], []}, MobableList),
Hence, you will get the new tuple as :
{[EVAL_SEQ_1, EVAL_SEQ_2, EVAL_SEQ_3, ...], [ListDataToConcat1, ListDataToConcat2, ListDataToConcat3,...]}
I'm not sure which sequence Number you want as you havn't mentioned it clearly, Here is the way you can get the minimum Sequence Number.
Evalsequence = lists:min(EvalSeq),
Now merge your code using merge function as shown below or you can refer merging inner list Merge inner lists of a list erlang:
MergedList = merge(MergingList),
And finally a separate list as:
[{Evalsequence, {<<"prvl_mobable_asset_0000_h200401">>, MergedList}}].
merge(ListOfLists) ->
Combined = lists:append(ListOfLists),
Fun = fun(Key) -> {Key,proplists:get_all_values(Key,Combined)} end,
lists:map(Fun,proplists:get_keys(Combined)).
I'm writing a game using Corona SDK in lua language. I'm having a hard time coming up with a logic for a system like this;
I have different items. I want some items to have 1/1000 chance of being chosen (a unique item), I want some to have 1/10, some 2/10 etc.
I was thinking of populating a table and picking a random item. For example I'd add 100 of "X" item to the table and than 1 "Y" item. So by choosing randomly from [0,101] I kind of achieve what I want but I was wondering if there were any other ways of doing it.
items = {
Cat = { probability = 100/1000 }, -- i.e. 1/10
Dog = { probability = 200/1000 }, -- i.e. 2/10
Ant = { probability = 699/1000 },
Unicorn = { probability = 1/1000 },
}
function getRandomItem()
local p = math.random()
local cumulativeProbability = 0
for name, item in pairs(items) do
cumulativeProbability = cumulativeProbability + item.probability
if p <= cumulativeProbability then
return name, item
end
end
end
You want the probabilities to add up to 1. So if you increase the probability of an item (or add an item), you'll want to subtract from other items. That's why I wrote 1/10 as 100/1000: it's easier to see how things are distributed and to update them when you have a common denominator.
You can confirm you're getting the distribution you expect like this:
local count = { }
local iterations = 1000000
for i=1,iterations do
local name = getRandomItem()
count[name] = (count[name] or 0) + 1
end
for name, count in pairs(count) do
print(name, count/iterations)
end
I believe this answer is a lot easier to work with - albeit slightly slower in execution.
local chancesTbl = {
-- You can fill these with any non-negative integer you want
-- No need to make sure they sum up to anything specific
["a"] = 2,
["b"] = 1,
["c"] = 3
}
local function GetWeightedRandomKey()
local sum = 0
for _, chance in pairs(chancesTbl) do
sum = sum + chance
end
local rand = math.random(sum)
local winningKey
for key, chance in pairs(chancesTbl) do
winningKey = key
rand = rand - chance
if rand <= 0 then break end
end
return winningKey
end